This invention relates to a method and apparatus for promoting the germination of plant seeds and improving the production of agricultural crops, particularly for accelerating the germination of the seeds, accelerating the growth of the crops and improving their quantity and quality.
It is known that irradiation of seeds and plants may have an effect on plant growth and development. This effect is not univocal: e.g., irradiation of plant seeds may accelerate or retard their growth.
WO 84/00693, generally directed to improving the growth rate and production of animals by irradiation, also mentions a method whereby lamps producing infrared light having wavelengths falling between 600-670 nm are used as a source of illumination for horticulture and plant production. What results are obtained by said method, is not stated. Further, no information is given relative to its parameters, except for the wavelengths, nor is any example described.
U.S. Pat. No. 4,914,858 proposes a method for fostering growth of plant-propagating material by irradiation by means of light-emitting diodes (LEDs) and states that by a correctly chosen wavelength, energy consumption can be reduced and plant growth can be furthered in entirely darkened, closed accommodations. While it is generally stated that the light spectrum of the light sources used may lie between 400 and 800 nm, viz., in the visible spectrum slightly and in part in the infrared, it is said that the spectrum of approximately 660 nm, viz., infrared light, is optimal for rapid germination of seeds. It is further stated that it is possible to use an intermittent light source at high frequency, because plants have a certain slowness in reacting to light and therefore the intermittent lighting is sensed as more or less continuous and the speed of germination is not adversely affected thereby. No other details as to the method and its results are given. An apparatus is shown in which seeds are accommodated in various trays and a group of lights is situated above each tray.
The aforesaid prior publications, and the art in general, do not provide sufficient data and parameters for obtaining an efficient promotion of germination of seeds and growth crops by means of lighting. They do not go beyond general suggestions and have not resulted in an agriculturally valid method for the said purposes. Nor do they describe an apparatus that can be used industrially for treatment of seeds in a controlled way and with an adequate production.
It is therefore a purpose of this invention to provide a method for accelerating the germination of seeds and promoting the growth of crops by the irradiation of the seeds.
It is another purpose of this invention to provide such a method that will provide the desired results with practically every kind of seeds.
It is a further purpose of the invention to provide such a method that is efficiently applicable on a productive agricultural scale.
It is a further purpose of this invention to provide an apparatus for carrying out the method of the invention on an industrial scale.
It is a still further purpose of this invention to provide such an apparatus which comprises means for controlling the relevant process parameters.
It is a still further purpose of this invention to achieve the aforementioned purposes at a limited cost, and with the light sources that are commercially available.
Other purposes and advantages of the invention will appear as the description proceeds.
According to the invention, the seeds to be treated are irradiated with radiation that is a simulation of the solar visible spectrum, viz., that approximates the solar spectrum in the visible range of wavelengths, which, as is known, is approximately from 400 to 700 nm. Suitable sources of such radiation are Xenon lamps. The light produced by the chosen lamps may have the desired spectrum. If not, filter means should be provided for filtering of IR and UV light. The presence of the filter means is desirable in any case in a pilot apparatus for the evaluation of the light sources and for the adjustment of process parameters to various types of seeds, but may be undesirable in an apparatus for continuous, high production.
The irradiating light is pulsed at a frequency that goes from about 10 to 150 pulses per minute, e.g., about 60 pulses per minute. The pulses are separated by intervals of no radiation, the length of which is preferably comprised between 10 and 90% of the duration of the pulses, and is preferably equal to the duration of the pulses. The seeds are cooled during the process, viz., during the radiation pulses and between them. Preferably they are cooled by means of a stream of gas, e.g., air.
As has been said, the solar simulation is preferably produced by means of xenon lamps. When a filter is used, the infrared portion of the radiation, if it comprises a substantial amount in the 800/1100 nm region, is preferably filtered off by means of a water filter. The ultraviolet radiation is filtered off by means of any known type of UV filter, such as are well known in the art.
Preferably, according to the invention, the seeds are subjected them to irradiance from 5,000 to 35,000 W/sqmt, e.g., 20,000 W/sqmt, for a period from 30 to 900 seconds, e.g., 180 seconds. The optimal radiation dose, irradiance and time of irradiation will depend on the type of seed, its shape, color, size, weight, thickness of shell and density, the volume of the individual seeds and the compactness of the seed bed, viz., the weight of seed per square meter of the fluidized seed bed. The temperature should at no time exceed 35xc2x0 C. in the seeds, to avoid damage thereto.
The invention further comprises an apparatus which comprises a solar simulator, means for exposing the seeds to radiation pulses, means for cooling the irradiated seeds and means for impelling the seeds to travel through the apparatus.
The means for exposing the seeds to radiation pulses may comprise means for activating the solar simulator or simulators by pulses, or screen means for intermittently intercepting the radiation, or mechanical or optical means for intermittently exposing the seeds to the radiation, or a mechanical or optical deviator device for deviating the radiation intermittently to different paths or portions of the seeds. In a preferred form of the invention, the radiation produced by a plurality of solar simulators is concentrated in a fixed region, and the seeds are caused to traverse said region repeatedly for short times, each such passage being equivalent to a radiation pulse.
The means for impelling the seeds to travel through the apparatus should be controllable, so to varyxe2x80x94other things being equalxe2x80x94the number of radiation pulses, their duration, the intervals between them and the overall amount of radiation directed on the seeds.
A preferred form of the apparatus according to the invention comprises a drum along which the seeds travel, a funnel or other feeder being provided to feed the seeds into the cylinder and a discharge at the end of the cylinder opposite to the feed. The drum is rotatable and is defined, in a preferred embodiment, by a plurality of longitudinal ribs and by a permeable sheath, e.g., made of netting, stretched over said ribs. The ribs engage the seeds, as the drum rotates, lift them from a lowermost position to an uppermost position, and let them fall when they reach this latter between guide surfaces, whereby they form a vertical layer. The permeable sheath permits the passage of a cooling gas, preferably air. Said structure of the drum, however, is not unique and could be substituted by a different structure, as long as this comprises means for entraining the seeds and apertures for the passage of a cooling gas. An elongated stationary structure, coaxial with the rotatable cylinder and of approximately the same length, hereinafter called xe2x80x9cenvelope,xe2x80x9d supports a plurality of light sources, preferably rod-like, axially oriented, Xenon lamps, and mirror surfaces so shaped as to concentrate the light of the lamps into a narrow axial strip, wherein the envelope is apertured to expose the falling seeds to the concentrated light. Air blower means is provided for blowing air from the discharge end of the cylinder to the feed end thereof, whereby to cool the seeds and exchange the air inside the machine. Rotatable cylinder and stationary drums are housed in a frame, which is provided with adjustable supports to permit to vary the slant of the drum and therefore the speed at which the seeds traverse it. Motor and control means and a power source are provided as required for the operation of the machine.
In another embodiment, feed means, such as a hopper or any convenient mechanism, feeds the seeds onto the top of the drum, and the drum raises them and carries them through an arc of its rotation, where they are exposed to radiation for a short time. The seeds are advanced longitudinally, viz., in a direction generally parallel to the axis of the drum, from their feed to a discharge by any convenient means that will be described, therefore the seeds are exposed to radiation repeatedly and each time for a short time at each turn of the drum rotation. Each such exposure constitutes a pulse of the radiation. A plurality of light sources, preferably rod-like, axially oriented, Xenon lamps, are mounted above the drum, and mirror surfaces are provided, so shaped as to concentrate the light of the lamps on the seeds retained at the top of the drum over a predetermined arc of said drum. The longitudinal advancement of the seeds is preferably caused in part by the fact that the drum is set at a small angle to the horizontal, being slightly higher at the feed end and lower at the discharge end. A cooling gas is preferably impelled to flow over the periphery of the drum and is preferably so directed as to cooperate to the advancement of the seeds.
In other embodiments of the invention, the seeds are advanced through the machine by mechanical or pneumatic conveyor means, so that they form two (or more) parallel strips of seed layers on one conveyor or on two (or more) parallel conveyors, and an irradiating light beam, optionally filtered, is directed alternatively to each of the two (or more) strips, whereby to produce a pulsed radiation.